A substrate processing apparatus is configured to perform specific processes such as a film forming process, an etching process and the like on a substrate to be processed (hereinafter, simply referred to as “substrate”) such as a semiconductor wafer, a liquid crystal substrate or the like.
As for such a substrate processing apparatus, there has been known a plasma processing apparatus, for example. The plasma processing apparatus includes, inside a processing chamber, a lower electrode serving also as a mounting table for mounting thereon a substrate and an upper electrode serving also as a shower head for injecting a gas toward the substrate. Such a parallel plate type plasma processing apparatus is configured to perform specific processes such as a film forming process, an etching process and the like with the use of a plasma generated by applying a high frequency power between both electrodes while supplying a specific gas through the shower head onto the substrate in the processing chamber.
In performing on the substrate specific processes such as a film forming process, an etching process and the like, there has been demanded to improve in-surface uniformity in processing the substrate by making processing characteristics (e.g., an etching rate, an etching selectivity, a film forming rate and the like) uniform in a surface of the substrate.
In such a view, in Japanese Patent Laid-open Application Nos. H8-158072 and H9-45624, there have been proposed techniques for supplying a processing gas of optional composition at an optional flow rate to plural portions on a substrate surface via gas supply lines individually connected with a plurality of gas chambers formed by dividing the inside of the shower head. In accordance with such techniques, the in-surface uniformity in etching the substrate can be improved by locally adjusting a gas concentration on the substrate surface.
A gas used for an actual substrate processing is obtained by mixing plural types of gases, e.g., a processing gas directly participating in a substrate processing, a gas for controlling a deposition of reaction products generated in the substrate processing, a carrier gas such as an inactive gas or the like, and the like. The types of gases are appropriately selected depending on target materials on the substrate or processing conditions. Therefore, there arises a need to perform a flow rate control by using a mass flow controller provided on each of the gas supply lines respectively connected with the gas chambers in the shower head, as disclosed in Japanese Patent Laid-open Application No. H9-45624.
However, in such a conventional configuration, although the gases supplied to plural portions on a substrate surface include common gases, each of the gases supplied from the gas chambers has its own gas supply system and, also, flow rates thereof are individually controlled. Accordingly, a line configuration and a flow rate control in each of the lines become complicated, which results in requiring a large space for the lines and an increased burden of control.
Further, even if the gases can be supplied from plural portions in the processing chamber by a simple control operation, when a flow rate ratio (distribution ratio) of the processing gases supplied from the plural portions changes due to a pressure variation, for example, during the introduction of the gases, the desired in-surface uniformity cannot be achieved. Hence, it is important to control the gas supply such that the process is prevented from being influenced by effects from the pressure variation and the like.